Q:
I live in New Jersey and it is getting cool here, with
temperatures in the upper 40s, but my tropical plant
collection is in a heated sunroom (still around 70s).
Should I continue fertilizing my plants? And if yes, my
second question about deciduous Sugar Apple tree. Should I
continue fertilizing it until it drops leaves?

A:
First of all, even though you live outside tropical
climate, your plants enjoy warm temperatures year round,
and can be treated like if they were in a Southern
garden.
Plant nutrients, both macro-elements (regular
fertilizer) and micro-elements (such as iron, manganese,
magnesium, copper, and other elements) play an important
role not only in overall plant health but also in plant
hardiness.
The rule of thumb is, even in warm climates we cut off
any fertilizer by the end of October. You still have
time for the last treatment this year (next will be in
March, or when your plants start showing new growth).
You may apply just a bit of slow-release granulated
fertilizer, or water-soluble by foliar spray, diluted
1/2 of label strength, to all evergreen species in your
collection.
The most important application before winter is
micro-elements and other plant boosters that will help
you plant collection survive winter months with a
shorter daylight and cooler temperatures. Now it is a
perfect time to make these simple steps:

Regarding your second question. Deciduous tropical
plants like Annonas, Adeniums, Plumerias, etc - do not
need regular fertilizer at this time, however, go ahead
and apply microelements Superfood complex, as well
as Sunshine-Honey, while
leaves are still green. These two will give a kick-start
to provide better flowering in spring, and production of
sweeter fruit later.